1. Field of the Invention
This invention relates to a blind, more particularly to a hollow built-in blind.
2. Description of the Related Art
Referring to FIGS. 1 to 3, a conventional hollow built-in blind 1 includes two glass plates 11, an annular spacer 12, a blind 13, an upper rail 14, a side frame 15 and a winding mechanism 16.
The annular spacer 12 is disposed between the glass plates 11, so that the glass plates 11 are spacedly parallel to each other. The spacer 12 and the glass plates 11 cooperatively define a receiving space 10.
The blind 13 is disposed in the receiving space 10, and includes a lower rail 131, a plurality of slats 132, two pull cords 133 each having one end connected to the lower rail 131 and the other end extending through the slats 132, and two cord ladders 134 corresponding to the pull cords 133 and used for turning the slats 132.
The upper rail 14 is disposed in the receiving space 10 above the blind 13, and has a U-shaped groove 141, and a PVC cover plate 142 covering the U-shaped groove 141.
The side frame 15 is disposed in the receiving space 10 and is located at one lateral side of the blind 13. The side frame 15 has a U-shaped groove 151, and a PVC cover plate (not shown) covering the U-shaped groove 151.
The winding mechanism 16 includes a slat turning unit 161, a blind actuating unit 162 disposed in the U-shaped groove 151 of the side frame 15, and an external control device 163. The slat turning unit 161 includes a transmission shaft 164 disposed in the U-shaped groove 141 of the upper rail 14, and two cord ladder turning devices 165 spacedly disposed on the transmission shaft 164 and respectively connected to the cord ladders 134. The blind actuating unit 162 includes an upper pulley 166 disposed on one end of the transmission shaft 164, a lower pulley 167 disposed on one end of the side frame 15 that is distal from the transmission shaft 164, an internal control device 168, a transmission belt 160 looped over the upper and lower pulleys 166, 167 and having two opposite ends respectively connected to the internal control device 168, and a spring 169 connected to the transmission belt 160 and the internal control device 168. The internal control device 168 is operable to move upward and downward in the U-shaped groove 151 of the side frame 15. The external control device 163 includes a guide rail 1631 fixed to an outer surface of the glass plate 11 that is adjacent to the PVC cover plates 142 and extending in a moving direction of the internal control device 168, an external controller 1632 disposed slidably on the guide rail 1631 and corresponding to the internal control device 168, and two magnets 1633 respectively disposed in the internal control device 168 and the external controller 1632. The external controller 1632 drives the internal control device 168 through magnetic attraction between the magnets 1633.
The other end of each pull cord 133 of the blind 13 is connected to the internal control device 168 after extending through the slats 132. Through the downward and upward movement of the internal control device 168 within the U-shaped groove 151 of the side frame 15, the pull cords 133 are pulled and released to raise and lower the lower rail 131 and the slats 132, respectively. When the slats 132 are lowered, the transmission shaft 164 is actuated by the upper pulley 166 to drive the cord ladder turning devices 165 to pull the cord ladders 134 and turn the slats 132 to an open or a closed position. During turning of the slats 132, the transmission shaft 164 cannot be activated by the upper pulley 166.
The pull cords 133 of the blind 13 pass along several turning points before connecting with the internal control device 168. This not only will cause the pull cords 133 to rub against the turning points and wear out and break, but also will cause the internal control device 168 to pull the pull cords 133 with difficulty so that the transmission efficiency thereof is low. Further, portions of the pull cords 133 in the U-shaped groove 151 of the side frame 15 will interfere with the operation of the transmission belt 160 which is connected to the internal control device 168, the upper pulley 166 and the lower pulley 167, so that the transmission belt 160 may slip on the upper and lower pulleys 166, 167 and the transmission thereof is not smooth.